Abstract

This thesis describes the application of multinuclear solid-state NMR to threematerials systems: first, components of polymer-based proton-exchange fuel cellsincluding the fluoropolymer membranes (Chapter 4) and the precious metal supportedcatalysts (Chapter 5); secondly, the formation of a complex bismuth niobiumaluminoborosilicate glass-ceramic with novel dielectric properties (Chapter 6);finally, platinum (II) dialkyldithiophosphates which belong to a class of compounds(metal dialkyldithiophosphates) some of which are used in mineral separationprocessing (Chapter 7).A full investigation into the effects of different conditions during samplepreparation and 19F NMR experiments on fluoropolymer membranes recommendedunmilled preparation, dry storage and magic angle spinning below 24 kHz for thestudy of structural differences between membranes. The application of 19F NMR to arange of commercial and experimental fluoropolymer membranes revealed that theequivalent weight does not affect the mobility of the polymer molecules such that canbe detected by this technique. Calculations of equivalent weight from 19F NMRdiffered with quoted values by up to 14%. Discrepancies were smallest in the shortsidechain polymers, as low as 3%. The assignment of spectra was invariant withsidechain structure apart from a change in the number of ester links. The presence orabsence of oxygen affected chemical shielding even around nuclei separated byseveral bonds. Differences in 1H linewidths between membranes could not beinterpreted without the control and comparison of manufacturing techniques. It isdesirable to remove the necessity for organic solvents in membrane casting. However,membranes cast from aqueous solution do not possess the same properties as thosefrom propanol. It had been proposed that rapid drying of water cast membranes wouldresult in a structure more similar to those from organic solvent. 1H NMR revealed thatthe opposite is the case, rapid drying makes the ordinarily more inhomogeneousaqueous membranes even more so. The application of both 19F and 1H NMR revealedthat the monomolecular layers of fluoropolymer deposited on the surface of fuel cellcatalysts to aid proton conductivity are categorically different in nature to the samematerials in the bulk state. 19F NMR suggests a polymer structure either moredisordered, greatly less mobile or both. 1H NMR displayed water environments thatcould not be reconciled to the standard model of rapid exchange between bulk waterand water associated with acid groups. Spectral differences caused by solvent andpolymer loading were discussed.The first complete and quantitative Fourier transformed 195Pt NMR spectra ofplatinum fuel cell catalysts, acquired using a field sweeping method, are analysed fordeviation from the cubooctohedral particle model and surface oxidation.A combination of 11B, 27Al and 29Si studies of the BN1 ceramic system afterdifferent temperature heat treatments confirmed much of the previous work on phaseevolution. However, it was shown that kyanite does not make up a significantproportion of the material until heat treatment reaches 1000 ºC and that aluminiumimpurities in bismuthbiobate crystals appear to increase with treatment temperature.The nature and abundance of glassy phases in the system are explored for the firsttime.Field sweep 195Pt NMR was employed to characterise the 195Pt chemical shiftanisotropy of five platinum (II) dialkyldithiophosphates complexes. Additionally the31P chemical shift anisotropies of two of the complexes, previously unpublished arepresented.